   [operator]
   (or (+where-operator-strings+ operator)
       (throwf "invalid operator: %s" operator)))
+
+(defn- where-nil-operator-sql
+  [operator]
+  (or (+where-nil-operator-strings+ operator)
+      (throwf "invalid nil operator: %s" operator)))
 
 (defn- where-exp-sql
   [model where-exp]


(def- +where-operator-strings+
  {:= "=", :> ">", :>= ">=", :< "<", :<= "<=", :not= "<>"})

(defn- where-conjunction-sql
  [conjunction]

    ; [:foo :> 20]
    :else
      (str "(" (name (where-exp 0)) " "
               (if (nil? (where-exp 2))
                 (where-nil-operator-sql (where-exp 1))
                 (where-operator-sql (where-exp 1))) " "
               (((quoters-by-name model) (where-exp 0)) (where-exp 2)) ")")))

(defn- where-sql
